The reasons for end-to-side coaptation: how does lateral axon sprouting work?

Abstract

Nerve fibers are attracted by sutureless end-to-side nerve coaptation into the recipient nerve. Opening a window in the epineurium enhances axon attraction and myelination. The authors analyze the features of nerve repair by end-to-side coaptation. They highlight the known mechanisms of axon sprouting and different hypotheses of start up signals (presence or absence of an epineurial window, role of Schwann cells, signaling from the distal trunk). The clinical literature is also presented and differences between experimental and clinical applications are pointed out. The authors propose their point of view and perspectives deriving from recent experimental and clinical experiences.

Keywords: Schwann cells; end-to-side nerve repair; epineurial window; glues in nerve repair; nerve babysitter procedures; nerve coaptation; nerve graft; nerve regeneration; nerve transfer; peripheral nerve repair; side-to-side nerve repair.

Figure 1

Representative high resolution light microscopic images of toluidine-blue-stained transverse sections of median nerve 36 weeks after end-to-side coaptation with N-butyl-2-cyanoacrylate. (A) Coaptation with an epineurial window; (B) coaptation without an epineurial window. With an epineurial window, the regenerated fibers are more numerous. Bars: 20 μm.